Muffle device



June 16, 19 6- F. P. KOBERT 2,644,504

MUFFLE DEVICE Filed Aug. 14, 1953 2 Sheets-Sheet 1 V/ J I fwwntur' Wat/$46.4

ATTORNEY June 16,' 1936. L F. P. KOBERT MUFFLE DEVICE Filed Aug. 14, 1933 2 Sheets-SheeLZ Fig.6

. application, filed on even date and bearing Ser- Patented June 16, 1936 UNITED STATES PATENT OFFICE MUFFLE DEVICE Application August 14, 1933, Serial No. 685,068

7 Claims.

the heating stage, scale will subsequently form on the surface of the heated portion of the blank as a result of this exposure. It has been found that if the portion of the blank being heated can be enclosed during the heating stage, particularly from the initial application of heat to the point of highest temperature, that the formation of scale on the surface is greatly reduced to the point where it is of considerably less importance, and in some cases entirely eliminated. This invention is therefore directed to means for enclosing that portion of a blank being heated for the full interval between the initial and the final application of heat, during which time this portion of the blank is almost entirely excluded from contact with circulating air, but at the same time providing sufiicient duct space for the expulsion of any gases liberated from the blank.

A further object is to provide a muffling device of this character which may be applied to the various types of blank gripping mechanisms used with electrical blank heating machines of the general character described in a copending ial No. 685,066.

A further object of this invention is to provide a mufiling device which will not interfere with the operation of the blank heating machine, which a does not introduce any electrical difiiculties therein, and which is of such simple construction that it may be readily adapted to existing machines or incorporated in newly designed machines without adding difficulties thereto.

Further and more specific objects of this invention will appear as it is more fully described, as will hereinafter follow:

In the form of this invention illustrated in the accompanying drawings,

Fig. 1 is an elevation showing the application of the invention to the gripping jaws of an electrical blank heating machine.

Fig. 2 is an end view of that shown in Fig, 1

showing the incorporation of a supporting liner in the muffle.

Fig. 5 is a view showing a combined muiile and blank heating electrodes.

Fig, 6 is a view along the lines 6-45 of Fig. '7.

Fig. '7 is a View along the lines 'I'I of Fig. 5.

Referring now to these figures, there is shown a pair of blank gripping jaws, I0 and I2, which form a part of an electrical heating machine, or the like, and gripped by these jaws is as shown a blank I4, the jaws Ill and I2 serving to effect electrical connection with the blank at their gripping points. In contact with one end of the blank I 4 isa longitudinally movable electrical contactor I8, which serves to complete the circuit through the blank for the purpose of passing current therethrough.

The contactor I6 is preferably arranged to move to the right, as viewed in Fig. 1 at the time of feeding a blank to the gripping jaws I0 and I2, and after the blank has been gripped by these jaws and presented to the contactor IE it moves into position to the left to effect electrical connection therewith by suitable application of pressure thereon. A form that the mufiler may take is indicated by the two semi-cylindrical members I8 and 20, each of which terminate in flanged portions 22 and 24, respectively, which flanged portions are suitably secured to each of the blank gripping jaws Ill and I2, as by screws I3, as indicated in Fig. 2.

As the blank I4 is gripped by the gripping jaws I0 and I2, the two mufiier halves I8 and 20 move together to encircle and enclose the blank I4 with a small intervening space between the blank and the inside walls of the muflier, thereby closing off possible circulation of air in this space, but leaving sufficient duct space to discharge gases and to prevent electrical contact therebetween. Similarly, a sufficient electrical clearance is maintained between the edges of the mufiier halves I8 and 20 and the contactor I6. The vertical opposing adjacent edges 30 and 32 of the muffler half portions I8 and 20, respectively, may be adapted to permit a slight gap therebetween when the gripping jaws I0 and I2 are in their closed position, so as to prevent the formation of a highly permeable magnetic path surrounding the current carrying portion of the blank I4,

thereby minimizing the heat generated within the mufiler members I8 and 20 due to the magnetic field established by the current, but this is not necessary. in all cases.

Repeated experiments and operations with a muffle of the character described have shown that blanks heated in connection therewith show only a slight formation of scale on the surface of the blank after upsetting or other operations thereon have been performed, and in many instances it has been observed that no scale whatever appears and that the surface was smooth and free from such. In many types of electrical heating machines it is desired to heat the blank in successive stages and between these stages there occurs what is commonly called a saturation period, during which time the heat generated within the blank is allowed to permeate the blank. It has been found that an application of a muffle of the type indicated to machines of this character has almost entirely done away with the subsequent formation of scale on the surface of the blank and has resulted in the production of a very superior product in this connection.

It will be quite obvious from the foregoing description that muffies of the type described may be made in a number of shapes and forms and may be applied to blanks in various and sundry ways, and that such mufiles are within the spirit and scope of this invention and the appended claims herewith. For example, the mufile may be an integral part of the blank gripping jaws, as shown in Fig. 3, in which the mufile halves and M are a formed part of the blank gripping jaws 42 and 43, respectively. An embodiment of this form of the invention is more clearly illustrated in a copending application filed on even date, bearing Serial No. 685,066, and disclosing a complete electrical blank heating machine.

When the portion to be heated of a relatively small diameter blank is long, the pressure exerted by the end contactor may be sufficient to cause the heated blank to be bent or take a permanent set. Such an effect is, of course, undesirable and the muffle devices which are described may have incorporated therein a supporting liner, such as that indicated at 44 in Fig. 4. As shown, this liner may be held against the inside face of the mufiie halves 45 and 46 and preferably has shoulders 48 projecting inwardly therefrom adapted to embrace at spaced intervals the portion of the blank being heated. This supporting liner is preferably made of some refractory material, such for example, as a lava compound. Where such a liner is used, the gap indicated at 50 between the two mufiie halves 45 and 46 may be increased slightly, or as desired, to provide sufficient duct space for expulsion of any gases liberated from the blank during heating.

Another form that the invention may take is illustrated in Figs. 5, 6, and '7, in which a pair of movable mufiling members 52 and 54 are each provided with longitudinal cavital recesses 56 and 58, and end plates 59 and Bil, the former being insulating and the latter metallic material. A metal blank, such as the blank indicated at 62, may be supported in these cavities against refractory supporting members 54 and 65. Current to the blank may be delivered through contacting electrodes 56 and 68, both of which may be adjustable with respect to the members 52 and 54, and locked by screws Ill. The refractory members B4 and 65 may likewise be adjustable and locked by similar screws 12, so that different size blanks may be accommodated. Also the contact members 65 and 68 may be disposed so that any given length of a blank may be heated. In addition a movable end contactor i4 may be used to contact with the end of the blank .62 where it is desired to heat a blank up to and including one end. A portion of the muffling body 54 supporting the electrode 66 is insulated from the remainder of the body by an insulating strip 51.

A very important result attached to the use of such muflle devices as described is that relating to the heat consumed in heating the blanks. It is found that with the use of such muffle devices, considerably less heat is required, since there is less heat lost to the surrounding air. It is found that in some cases as much as 25% less energy is required when heating blanks enclosed by such a muffle than when not enclosed by a muffle.

What is claimed is:

1. In a mufile device adapted for use on an electric .blank heating machine having a pair of relatively movable electrodes adapted to grip a portion-of the blank to be heated, the mufile device comprising a plurality of portions associated with said movable electrodes and movable therewith, the mufile portions projecting from said electrodes and being adapted to substantially enclose a portion of a blank gripped by said electrodes to substantially prevent the circulation of air adjacent the surface of such portion of the blank.

2. In a muffle device adapted for use on an electric blank heating machine having a pair of relatively movable electrodes adapted to grip a portion of a blank to be heated and to have a portion of the blank projecting from the port-ions of the electrodes eng-ageable with the blank, the mufiie device comprising a plurality of portions associated with the movable electrodes, the muffle portions projecting from the electrodesand being adapted'to substantially enclose a portion of a blank gripped by said electrodes to substantially prevent thecirculation of air adjacent the surface of such portion of the blank.

3. In a muffle device adapted for use on an electric blank heating machine having a pair of relatively movable electrodes adapted to grip a portion of a blank to be heated and to have a portion of the blank projecting from the port-ions of the electrodes engageable with the blank, the mufile device comprising a pair of substantially semi-cylindrical members, one of said'membersbeingsecured to each of the movable electrodes and movable therewith, the muffle portions projecting from the electrodes and being adapted to substantially enclose a portion of a blank gripped by said electrodes to substantially prevent the circulation of air adjacent the surface of such portion of the blank.

4. In a mufile device adapted for use on an electric blank heating machine having a pair of relatively movable electrodes adapted to grip a portion of a blank to be heated and having a contactor adapted to engage the work blank at a point spaced from the portion gripped by the relatively movable electrodes, the mufile device comprising portions associated with the movable electrodes and movable therewith, each of said portions projecting from an electrode towards said contactor and extendingsubstantially the entire distance intermediate the electrode and the contactor, the mufile portions being adapted to substantially enclose the portion of the blank intermediate the electrodes and the contactor to substantially prevent the circulation of air fadjacent the surface of such portion of the blank.

5. In a muflle device adapted for use on an electric blank heating machine having a pair of relatively movable electrodes adapted to grip a portion of the blank to be heated, the muflle device comprising a plurality of portions associated with said movable electrodes and movable therewith, the muflie portions projecting from said electrodes and being shaped to substantially enclose a portion of a blank gripped by said electrodes and thus to substantially prevent the circulation of air adjacent the surface of such portion of the blank, each of said mufile portions carrying a refractory member having projecting shoulders adapted to engage a portion of said blank to support said blank.

6. In a mufile device adapted for use on an electric blank heating machine having a pair of relatively movable electrodes adapted to grip a portion of a blank to be heated and having a contactor adapted to engage the work blank at a point spaced from the portion gripped by the relatively movable electrodes, the muffle device comprising portions associated with the movable electrodes and movable therewith, each of said portions projecting from an electrode towards said contactor and extending substantially the entire distance intermediate the electrode and the contactor, the mufile portions being adapted to substantially enclose the portion of the blank intermediate the electrodes and the contactor and thus to substantially prevent the circulation of air adjacent the surface of such portion of the blank, each of said muffle portions having a refractory member associated therewith and shaped to engage a portion of said blank to support said blank.

7. In a muffle device adapted for use on an electric blank heating machine having a plurality of blank gripping and carrying electrodes, a contactor positioned adjacent said blank gripping and carrying electrodes and engageable with a blank carried thereby, and having means for moving the blank gripping and carrying electrodes past said contactor, the muflie device being of size and shape adapted to substantially enclose the portion of a blank intermediate the blank gripping and carrying electrodes and the contactor to substantially prevent the circulation of air adjacent the heated surface of such enclosed portion of the blank and comprising members 20 mounted upon the blank gripping and carrying electrodes and movable therewith.

KATHRYN KOBERT, Administratriw of Frank P. Kobert, Deceased. 

